TCMS (Train Control and Management System) is the core of train operation, which carries several critical services, such as traction power, auxiliary power, speed, location, braking, door control, HVAC, train status monitoring and diagnosis. With the popularity and maturity of Ethernet technologies, an IP based TCMS and related specifications such as ETB (Ethernet Train Backbone) and ECN (Ethernet Consist Network) are de!ned in IEC61375.